"Zoo" is a cool sensibility married to a hot topic, a poetic film about a forbidden, unsettling subject. Elegantly made and eerily lyrical, it deals with what director Robinson Devor has accurately called "the last taboo, the boundary of something comprehensible." It's a subject so unnerving that just the notion of it can send people over the edge.

The details of the events referred to in this documentary would once have been too graphic to put in a family newspaper, but when the Seattle Times broke the news in July 2005 of a man in the rural town of Enumclaw, Wash., dying after having sex with an Arabian stallion, the resulting stories were the most-read articles in the paper's history.

The ensuing furor led inexorably to questionable humor and what Devor calls "the prurient spectacle," but the filmmaker, who along with writing partner Charles Mudede, lives in Seattle, was surprised to find that "nobody did an in-depth look at this, that there was no investigative reporting rounding the story out with psychology." Which is what "Zoo" does.

As neutral as it is possible to be with a subject so inflammatory, "Zoo" is notable as much for what Devor, who said at Sundance that he'd "aestheticized the sleaze right out of it," doesn't include in his film as for what he does.

"Zoo" doesn't deal with the legal or animal-cruelty issues its subject raises. There are few conventional documentary talking heads and, except for an almost subliminal glimpse of a few seconds of video, the sexually graphic is absent. Yet just the act of making a film about something so provocative is sure to be a provocation both for people who want more details and those who demand overt condemnation.

"Zoo," however, has something else on its mind. It takes its name not from a place to take the kids but rather a term of self-identification used by the zoophile community, as in "being zoo." The film's idea is to explore, in the classic "nothing human is alien to me" fashion, a lifestyle that is almost impossible to wrap your mind around, to give voice to people who understandably are never heard from.

Given all that, it was a masterful idea to begin "Zoo" with a disconcerting, disorienting scene. The film opens with a black screen with only a little dot of light visible. Slowly, over a minute and a half, the camera shakily moves toward the light until its finally clear that what we have been seeing is the opening of a mine shaft approached from deep within the Earth.

While three "zoos" agreed to talk on audiotape about their lifestyle, none used real names and only one, called Coyote, agreed to appear on camera. Coyote was born and raised in the coal mining area of Virginia, hence the opening shot, and he talks about connecting to the zoophile community through the Internet and how fellow zoos encouraged him to move to Washington state, which at the time (the laws have since been changed) did not have anti-bestiality statutes.

Though we hear Coyote's tape-recorded voice and see him, he does not talk to the camera: what we see are re-creations of episodes from his life. A similar technique is used for the other two zoos, nicknamed "H" and "The Happy Horseman," with the difference being that in these cases, their actions are re-created by actors.

"Zoo" also re-creates scenes from the life of the man who died, known here as "Mr. Hands," an engineer for Boeing. His friends rushed him to an emergency room and left him there, only to be tracked down by the police after security cameras recorded the license plate of the truck they used.

The key "Zoo" participant who does speak directly to the camera is Jenny Edwards of Hope for Horses, an organization that takes in neglected and abused animals. She was called in to deal with the horse involved in Mr. Hands' death and, in an unsettling re-creation, prepares to geld it.

The thoughts and actions of the zoos are extremely difficult to assimilate. Coyote says that he doesn't "need a high level of emotional interaction, be it human or otherwise." The other zoos mightily resent being thought of as evil and insist "you're connecting with another living being who is very happy to participate."

Director Devor, whose previous film was the unusual and evocative "Police Beat," places words like these against elegiac, stunningly beautiful visuals that accentuate the spooky, almost hypnotic beauty of the Pacific Northwest. "I count on the natural world pulling my films through," the filmmaker said at Sundance. "I thought the marriage of this completely strange mind-set and the beauty of the natural world could be something interesting." And that, to put it mildly, is what it has turned out to be.